Cooled blades for gas turbines, in which the cooling air, which is guided inside the blade airfoil in convoluted cooling passages, is fed by means of a feed hole arranged on the blade shank, are known, for example, from U.S. Pat. No. B2-7,264,445, which is incorporated by reference. Such feeds can also open into the outside space at the side on the shank (see, for example, U.S. Pat. No. 4,940,388, which is also incorporated by reference).
The feed holes in the shank of the blade create mechanical stress concentrations on the edges, which can be detrimental to the service life of the blade. In highly loaded blades, as are used in turbines of large aircraft, for example, measures are therefore taken to reduce these stress peaks on the edges of the hole openings. Such a measure is to provide for example on the shank 20, according to FIG. 2, around the feed hole 21, a bead 22 which encompasses the opening. Such a blade is described in an article by T. Sourmail, “Coatings for Turbine Blades”, University of Cambridge, in the section “Coatings” on p. 6.
The stress-reducing bead around the opening of the feed hole leads to an increase of the service life, but, on account of its localization, has practically no effect upon the vibration behavior of the blade. It would, however, be desirable to achieve an additional improvement in the vibration behavior.